Antioxidants for mineral oil lubricants and compositions containing the same



Patented Nov. 30, 1948 2,454,890 ICE 2,454,890 ANTIOXIDANTS FOR MINERALOILv LUBRI- CANTS AND COMPO THE SAME SITIONS CONTAINING Herschel G.Smith, Wallingford, and Troy L. Cantrell, Lansdowne, Pa... and John G.Peters, Audubon, N. J., assignors to Gulf Oil Corporation, Pittsburgh,,vania 2a., a corporationof Pennsyl- No Drawing. Application April 9,1947,

. Serial No. 740,482

This invention relates to antioxidants for mineral oil lubricants andcompositions containing the same, and more particularly, it relates toaddition agents for mineral oil lubricants which in- 3 hlbit theoxidative deterioration oi' said lubricants.

In the lubrication of internal combustion engines of all types,particularly when severe operating conditions are encountered, plainmineral lubricating oils often prove unsatisfactory in service becauseof the oxidative deterioration of the oil, with the attendant depositionon the engine surfaces of varnish, gum or sludge. Furthermore, manylubricating oil compositions which may be highly satisfactory for thelubrication of other mechanisms have been found wholly unsuitable foruse as turbine oils.

The formation of varnishes, gums and sludges on engine surfaces is dueat least'in part to oxidation effects on mineral lubricating oils. Inturbine oils the problem of oxidation is further aggravated, because innormal use turbine oils rapidly become contaminated with water.

It is an object of this invention, therefore, to provide an additionagent for mineral oil lubricants which will inhibit the oxidativedeterioration of such lubricants.

It is further an object of this invention to pro- 16 Claims. (Cl.252-515) 2 for the condensation ranges from 150 to 300 F. Theproportions of the'reactants may vary over a relatively wide range. Thebenzyl benzoate may be employed in an amount of from 1 to 4 mols; N-

dimethylaniline may be employed in an amount 01 1 from 1 to 6 mols; andthe amount of formaldehyde may range from 0.5 to 6 mols of formaldehydeper mol of benzyl benzoate. Ordinarily, it is preferred to use from-5 to10 per cent by weight of the activated clay catalyst, based on the totalweight of the reactants. However, smaller amounts, as low as 1 per centby weight, and larger amounts, as high as 20 per cent by weight, mayalso be employed; but larger amounts than about 10 per cent by weightare ordinarily not necessary. a

In lieu of formaldehyde any formaldehydeyielding compound, such asparaformaldehyde,

dioxymethylene and trioxymethylene may be employed. In such case, theamount of formaldehyde-yielding compound used is based on the equivalentnumber of mols of formaldehyde yielded within the range of proportionsof formaldehyde set forth hereinabove. Accordingly, as used in theappended claims, the term formaldehyde is intended .to includeformaldehyde-yieldvide improved mineral oil lubricantcompositions whichare remarkably stable against oxidation under service conditions.

. These and other objects are accomplished by the present inventionwherein an addition agent for mineral oil lubricants is prepared bycondensing benzyl benzoate, N-dimethylaniline and formaldehyde in thepresence of an activated clay catalyst. and recoveringthe condensationprod uct. The condensation product so obtained is a light-coloredproduct which, when added to mineral oil lubricants, confers aremarkable stability against deterioration by oxidation. Suchcondensation products and mineral oil lubricant compositions containingthem are believed to be novel and are considered parts of our invention.Contrary to what may be expected from the nature of t he reactants, wedo notobtain highly-condensed. .insoluble resinous products.- On thecontrary,

ing compounds as well as formaldehyde itself.

Various activated clay catalystsmay be employed in accordance with ourinvention. Such materials are well known in the art and comprise anatural clay, such as bentonite, fullers earth, floridin and smectite,which has been acid treated in order to activate the clay.

In preparing our new addition agent the reactants and catalyst areplaced into a reaction vessel which is then closedand the mixture isheated with agitation until all of the formaldehyde orformaldehyde-yielding compound has been consumed. At this time the waterwhich is formed as a result of the condensation is removed, preferablyunder vacuum, and the dehydrated condensation product is then filteredto remove the activated clay catalyst. In some instances, it isdesirable to prepare our new addition agent in a. concentrate in amineral lubricating oil which may then-be diluted down with additionaloil to the concentration desired in the final lubricating composition'In such instances, the mineral lubricating oil may be added in asuitable amount, say in a weight equal to the weight of reactants, tothe reaction mixture in the reaction vessel, and the condensationproduct obtained will then be a concentrated solution of the additionagent in the mineral lubricating oil.

The condensation products obtained in accordance with our invention areliquids or crystalline solids. While we do not desire to be boundby anytheory as to the reaction or reactions involved s,404,aao

or the chemical composition of the products, we believe that irr view ofthe multiple points of the respective molecules at which the reactantsmay aqueous) and 8.2 per cent by"weight of the total reactants of anactivated clay catalyst. The mixture was refluxed and agitated at 220 F.for a period of twelve hours. The temperature was then raised to 280 F.and all water, both that added with the formaldehyde and formed in thereaction, was distilled off. The product was then filtered and had thefollowing properties:

' Gravity: API

Color. NPA 1 1.75 Neutralization No 0.44

Example IL-An addition agent was prepared by reacting 2 mols of benzylbenzoate, 1 mol of N-dimethylaniline and 2 mols ofiformaldehyde in thepresence of 5 per cent by weight of the total reactants of an activatedclay catalyst under the conditions set forth in Example I. The producthad the following properties: i,

Gravity: API

1.8 Color, NPA 1.5 Neutralization No 0.60

Example II I.-An addition agent was prepared by reacting 2 mols ofbenzyl benzoate, 4 mols of N-dimethylanilineand 6 mols of formaldehydeagents. In the following examples, the base oil and the same oil blendedwith our new addition agentsare subjected to a standard oxidation testwhich measures the stabilitly of the oils to oxidation. The oxidationtest referred to is a standard test described in "ASTM Standards'onPetroleum Products and Lubricantsflf September1943, pages 17-20.Briefly, the test comprises subjecting the .011 sample to oxygen at atemperature of 05 C.

(203. F.) in the presence of water and an ironcopper catalyst, anddetermining the time required to build up a neutralization number of 2.The flow of oxygen is maintained at 3 liters per hour. The remarkablyeflective stability to ox-,

idation of mineral oil lubricant compositions containing our newaddition agents is illustrated by the results shown in the followingexamples.

& Example IV.To a motor oil, which had been highly refined by analuminum chloride treatment, there was added 0.5 per cent by weight ofthe addition agent prepared in accordance with Example I. A comparisonof the base oil and improved oil follows:

Base Oil Improved Oil Gravity: API 29.8 29.6 Viscosity. SUV, 210 F 78.076. 8 Color, PA 2. 0 2. 6 Neutralization No 0.01 0. 02 Oxidation Test,ASTM Proposed 203 F. 8 L. 0 gen per Time 0 dined. no 3500+Neutralization No 2. 0

As shown in this example, the improved oil had an oxidation stability ofmore than 3500 hours, but

, the neutralization number had not yet reached 2.0.

in the presence of 6 per cent by weight of the total reactantsof anactivated clay catalyst under the conditions set forth in Example I.-The product had the following properties:

Gravity: API 2.4 Color, NPA I 2.0 Neutralization No 0.52

The condensation products obtained in accordance with the abovedisclosure from benzyl benzoate. N-dimethylaniline and formaldehyde inthe presence of an activated clay catalyst are excellent addition agentsfor mineral oil lubricants. They are readily soluble'in'all types ofmineral oils, that is, paraillnic, naphthenic or mixed base mineral oilsand can be blended with mineral oils in high 5 proportions toformconcentratedsclutions thereof, which may then be diluted down to theproportions desired in the final mineral oil lubricant composition. Asstated, our new addition agents are remarkably eil'ective'in inhibitingthe oxidatlve deterioration of mineral oil lubricant compositions. Forthis purpose small amounts of our new addition agents are generallysufllcient. For example, our addition agents maybe added to min-' erallubricating oils in minor amounts, say from 0.001 to l per cent byweight on the mineral oil,

suflicient to inhibit the oxidative deterioration-of.

the oil. Larger-amounts of our new addition agents may be used ifdesired but it is ordinarily unnecessary to do so. j

The following examples illustrate the remark- Example V.-An improvedsteam turbine oil was prepared by adding 0.5 per cent by weight of theaddition agent prepared in accordance with Example II to a turbineoilbase. A comparison of the base oil and the base oil blended with theantioxidant showed the following results:

Base Oil Improved Oil Gravi =irr.'.- 2st 28.5 0x ide t 11 Iest, .ad'llProposed 203 x n r rum Oxidfiedj Hrs 180 0000+ Neutralization No"... 2.0

Here again, the improved oil showed an oxidation stability of more than3000 hours, but the neutrallzation number had not yet reached 2.0.

The above examples show the remarkable oxidation stability imparted tomineral oil lubricant compositions by the use of our new additionagents. Mineral oil lubricant compositions containing our new additionagents are therefore hydroxybutanal) for formaldehyde.

eminently suited for use where the operating conditions are extremelysevere, as in Diesel, tank and truck engines, and in the lubrication ofsteam turbines. F

The remarkable effects of our new addition agents cannot be readilyaccounted for and can- ;not be predicted from the nature of thereactants. Thus. condensation products prepared from .other functionallysimilar compounds have been found to be either prooxidant or to show noantioxidant eflects whatsoever. For example, we

have prepared a condensation product similar to our new addition agentby substituting aldol (3- The resulting condensation product was foundto be entirely unsuitable for inhibiting the oxidative deterioraableantioxidant ei'iects or our new add tion 76 tlonof mineral oil lubricantcompos ons.

' tion product being 1' to 6 mols of N-diinethylaniline and 0.5 to 6mols of formaldehyde per mol of benzyl benzoate in the presence 'ofan'activated clay catalyst at a temperature not in excess of 350 F., andrecover?- ing the condensation product.

2. The process of preparing an addition agent for mineral oil lubricantswhich comprises condensng from 1 to 4 mols of benzyl benzoate, 1 to 6mols of N-dimethylaniiine and 0.5 to 6 mols of formaldehyde per mol ofbenzyl benzoate in the presence of 5 to per cent by weight on the totalreactants of an activated clay catalyst at a temperature of from 150 to300 F-., and recovering the condensation product.

3. The process of preparing an addition agent for mineral oil lubricantswhich comprises adding from 1 to 4 mols of benzyl benzoate, 1 to 6 mols,

of N-dimethylaniline, 0.5 to 6 mols of formaldehyde per mol of benzylbenzoate, and an activated clay catalyst to a mineral lubricating oil,heating the mixture to a temperature not in excess of 350 F. to form acondensation product, and recovering a solution of the condensationproduct in the mineral lubricating oil. a

4. The process of preparing an addition agent 'for mineral oillubricants which comprises condensing 1 mol of benz'yl benzoate, 6 molsof N-dimethylaniline, and 6 molsof formaldehyde in the presence of about8 per cent by weight on the total reactants of an activated claycatalyst at a temperature of from 150 to 300 F.. and recovering thecondensation product.

5. The process of preparing an addition agent for mineral oil lubricantswhich comprises condensing 2 mols of benzyl benzoate, 1 mol of N--dimethylaniline and 2 mols of formaldehyde in the presence of about 5per cent by weight on the total reactants of an activated clay catalystat a temperature of from 150 to 300 F., and recovering the condensationproduct.

6. The process of preparing an addition agent for mineral oil lubricantswhich comprises condensing 2 mols of benzyl benzoate, 4 mols oiN-dimethylaniline and 6 mols of formaldehyde in the presence of about '6per cent by wei ht on the total reactants of anactivated clay catalystat a temperature of from 150 to 300 F., and recoverin; the condensationproduct. a

'7. A non-resinous condensation product of from 1 to 4 mols of benzylbenzoate, 1 to 6 mols oi N dimethylaniline and 0.5 to 6 mols offormaldehyde per moi of benzyl benzoate, said condensaobtained by theprocess of claim 1. v

8. A non-resinous condensation product of 1 moi of benzyl benzoate, 6mols or N-dimethylaniline and 6 mols 0! formaldehyde, said condense--tion product being obtained by the Process or claim 4.

9. A non-resinous condensation product of 2 mols oi benzyl benzoate, 1mol oi-N-dimethyianiline and 2 mols of formaldehyde, said condensationproduct being obtained by the process of claim 5.

10. A non-resinous condensation product of 2 mols of benzyl benzoate, 4mols of N-dime'thylani- 3 line and 6 mols of formaldehyde, saidcondensa- I amount, sufficient to inhibit the oxidative de.--

terioration of said 011 of a non-resinous condensertion'product of from1 to 4 mols of benzyl benzoate, 1 to 6 mols of N-dimethylaniline and 0.5

to 6 mols of formaldehyde per mol of benzyl ben-' zoate, saidcondensation productbeing obtained by the process of claim 1. v

13. A lubricant composition comprising a major am'ountof a. minerallubricating oil, and a minor amount, from 0.001 to 1.0 per cent byweight of said'oil, of a non-resinous condensation product of from 1 to4 mols of benzyl benzoate, 1 to 6 mols of N-dimethylaniline and 0.5 to 6mols or formaldehyde per mol of benzyl benzoate, said condensationproduct being obtained by the process of claim 1.

14. A lubricant composition comprising a major amount or a minerallubricating oil, and a minor amount, suiiicient to inhibit the oxidativedeterioration of said oilof a non-resinous condensation product of 1 molof benzyl benzoate, 6 mols oi N-dimethylanillne and 6- mols offormaldehyde, said condensation product being obtained by the process ofclaim 4.

15. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, sufficient to inhibit the oxidativedeterioration of said oil of a non-resinous condensation product of 2mols of benzyl benzoate, 1 mol of N -dimethylaniline and 2 mols offormaldehyde,

said condensation product being obtained by the process of claim 5.

16. A lubricant composition comprising a major amount of a minerallubricating oil, and a minor amount, suilicient to inhibit thevoxi'dative deterioration of said oil of a non-resinous condensationproduct of 2 mols of benzyl benzoate, 4 mols of N-dimethylaniiine and 6mols of formaldehyde,

said condensation product being obtained by theprocess of claim 6.'

HERSCHEL G. SMITH. TROY L. CANTRELL,

JOHN G. PETERS.

1 REFERENCES CITED The following references are of record in the file ofthis patent:

unrrnn STATES PATENTS

